Most of so-called large or big square balers in use work according U.S. Pat. No. 4,372,104, wherein a pick-up device loads harvested agricultural material into a supply passage, connected to the inlet opening of a compressing channel. A pressing ram is reciprocated back and forth in a horizontally arranged compressing channel by at least one plunger for compacting the material to a big square bale up to a weight of one ton. Usually, the drive assembly of the plunger is a pitman-and-crank-assembly coupled to a gear-box, as shown in U.S. Pat. Nos. 4,525,991 or 4,782,651, respectively. These drive means are rather voluminous and have many components, thus being relatively expensive to produce.
The agricultural material is moved through the supply passage to the compressing channel by a conveying or feeding device extending into the supply passage with a plurality of fork-like fingers or tines. The crop entering the compressing channel, is only partially compressed by the tines of this feeding device, and oscillates in a kidney-shaped path of travel. Thus the main compacting work has to be done by said pressing ram, which has to be very strongly built. Furthermore, the drive means of the feeding mechanism is rather complicated.
As the agricultural material has a certain elasticity when compressed, the compressed material re-expands upon the return movement of the reciprocating ram. Thus, with this method the material is compressed several times, causing a loss of energy, and the degree of compression is relatively low due to the re-expansion of the material.
The German Patent No. 34 45 015 discloses a rotary compressing drum with tines, the tips of which engage grooves in the drum casing, thus shredding and crushing the material. In this way a densified layer is produced, which is accumulated in a box to a rectangular bale.
Although the degree of compression is higher than with the above-mentioned usual big balers, it is desirable to improve the density to achieve highly densified bales which may be transported and stored within a minimum space.
Furthermore, the forming of a rectangular bale according to the German Patent No. 34 45 015 is very complicated, as the layers are piled up in a generally vertical box by lowering the ground-plate of this box step-by-step. Thus, the size of the accumulated bale is very difficult to change. After forming one big bale consisting of about ten to twenty layers the ground-plate has to be lifted in only a few seconds, as the feeding of the material is continuous. The doors of the box have to be opened and the knotting device has to be operated by a very complicated hydraulic control circuit. Thus, continuous, fast operation of the crop-baler is very difficult to achieve.